Such instruments, for example, hand-held, battery powered, self-contained pyrometers, utilize a laser-generated beam for the purpose of striking a surface or other target and thereby indicating to the user that the instrument is properly aligned. It is known in the art of laser-aimed instruments to project a single laser beam to create a spot of laser light on the target at a desired central point of the area of the target under investigation or treatment.
The beam should be sufficiently powerful to illuminate the spot on the target so as to be clearly visible to the user of the instrument over a range of distances and under various ambient light conditions. However, it is not possible simply to increase the power of the beam to cope with relatively long distances and bright ambient light conditions. This is because there are legal and practical restrictions on the use of laser beams because of the possible danger to the user, e.g. risk of damage to eyesight. There are regulations and standards which provide different classifications for a product capable of generating a laser beam. There are, in the United States, two laser produce classifications that are used in industry in terms of, for example, infra-red temperature measurement:
1. Class 2: The laser power output of the device at 20 cm away and having a 7 mmperture should be less than 1 mW. Wavelength range: 400 to 700 nano-meters.
2. Class 3A: The laser power output of the device at 20 cm away and having a 7 mm aperture should be less than 5 mW. Wavelength range: 400 to 700 nano-meters.